iphone - Unrecognized selector sent to class in OAuthCore class -

I have created a library project, in which I am trying to share Twitter. But when I try on Twitter, the application crashes on the following line

  NSString * _oAuthNonce = [NSString ab_GUID];   
 By error:  
 
 + [NSString ab_GUID]: Unknown selector has been sent to class 0x1a09fd8   
 Ab_GUID This method is present in the  OAuthCore  category  
  + (NSString *) ab_GUID {CFUUIDRefU = CFUUIDCreate (kCFAllCatorDefault); CFStringRef s = CFUUIDCreateString (KCFLocetter Default, U); CFRelease (U); Return [[NSString *] S. Autorex]; }   
 (All of my classes are present in the static library)   
 
 
 Did you  & lt; OAuthCore / OAuth + Additions.h & gt; Imported? It looks like  & lt; OAuthCore / OAuthCore.h & gt; It will not automatically be included on .  
 Also make sure that the compilation is done in the stable library.